Although blood gases temporarily improved due to an immediate blood flow redistribution, there is still a delayed capillary-alveolar fluid transfer and pulmonary edema formation. CsA increased PaO2/FiO2 ratio and decreased CO2 gradient in a dose-dependent manner. Such gas exchange improvements could be due to an enhancement of the hypoxic pulmonary vasoconstriction mediated by CsA. Furthermore, lung IRI observed during the primary graft dysfunction was similar to those GSK-3 inhibitor found in the ARDS [11, 40]. The heterogeneous lesions from the alveolar epithelial tissue and the pulmonary capillary bed features microvascular obstructions accompanied by cellular fragments and microthrombi. The heterogeneity of these

types of lesions has been shown through histological analyses in ARDS [48], IRI [13], and also by clinical surveys showing various radiologic infiltrations in a patient’s pulmonary transplant [32]. IRI is a heterogeneous pulmonary vasoconstriction that

leads to a redistribution of pulmonary blood flow from injured lung zones to normal lung areas. Many works highlight the importance of hypoxic vasoconstriction in maintaining oxygenation during acute lung injury [4, 44]. This vascular reactivity limits the ventilation and perfusion mismatch, reduces the alveolar dead space, and consequently improves oxygenation. We assumed that a part of Bcl-2 inhibitor the gas exchange improvements observed earlier in our CsA treated lungs were related to such blood redistribution. CsA could possibly restore the capillary-alveolar

barrier function. Indeed, several publications on IRI lung models have shown that CsA was able to diminish the secretion of pro-inflammatory mediators [15, 30] and decrease all lung vascular permeability by more than 50% relative to the animals in the control group [25]. Such effects may have reduced edema formation and improved gas exchanges throughout the capillary-alveolar membrane. With this hypothesis, we consistently noted a trend in alveolar epithelial function improvement with low (1 μM) and moderate (10 μM) doses of CsA. In these groups, CsA seemed to increase the rate of AFC and decreased RAGE level in BAL fluid. These two parameters have been shown to reflect lung status after ischemia-reperfusion [7]. However, cytokine concentrations were evidently worsened in lungs treated with 30 μM of CsA, which was similar to their elevated lung vascular pressure and resistance, although the PaO2/FiO2 ratio and CO2 gradient were high in those lungs. We conclude from these observations that CsA has a preeminent vasoconstrictive effect on lung vasculature compared to its other actions. Low doses of CsA may have beneficial anti-inflammatory and anti-apoptotic effects, whereas high doses of CsA (30 μM) may display hemodynamic effects. Moreover, in our data, the venular resistances (i.e., post-capillary bed) were enhanced by CsA administration.